首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   32064篇
  免费   1817篇
  国内免费   154篇
耳鼻咽喉   293篇
儿科学   426篇
妇产科学   343篇
基础医学   4264篇
口腔科学   990篇
临床医学   2083篇
内科学   7713篇
皮肤病学   845篇
神经病学   2218篇
特种医学   1272篇
外科学   5673篇
综合类   158篇
一般理论   1篇
预防医学   998篇
眼科学   642篇
药学   2451篇
中国医学   52篇
肿瘤学   3613篇
  2023年   140篇
  2022年   309篇
  2021年   542篇
  2020年   326篇
  2019年   399篇
  2018年   516篇
  2017年   476篇
  2016年   506篇
  2015年   548篇
  2014年   714篇
  2013年   906篇
  2012年   1345篇
  2011年   1487篇
  2010年   862篇
  2009年   786篇
  2008年   1323篇
  2007年   1326篇
  2006年   1361篇
  2005年   1450篇
  2004年   1340篇
  2003年   1361篇
  2002年   1289篇
  2001年   1294篇
  2000年   1326篇
  1999年   1197篇
  1998年   403篇
  1997年   345篇
  1996年   312篇
  1995年   300篇
  1994年   268篇
  1993年   259篇
  1992年   831篇
  1991年   747篇
  1990年   738篇
  1989年   703篇
  1988年   717篇
  1987年   627篇
  1986年   616篇
  1985年   600篇
  1984年   401篇
  1983年   326篇
  1982年   154篇
  1979年   322篇
  1978年   205篇
  1977年   153篇
  1975年   149篇
  1974年   213篇
  1973年   151篇
  1972年   166篇
  1971年   149篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
71.
Pseudopodia of capillary endothelium in ocular tissues   总被引:1,自引:0,他引:1  
The frequencies of pseudopodia projecting from capillaries of various parts of the eye were observed in 16 human eyes with a transmission electron microscope. The pseudopodia were found mainly projecting from the choriocapillaris and rarely seen in the retina, iris or ciliary body. The frequencies of pseudopodia from the choriocapillaris were not correlated with the localization in the fundus (macular area or peripheral fundus), age, sex, time elapsed between death or enucleation and fixation. The significance of pseudopodia from the choriocapillaris is unknown. However, there is the possibility that pseudopodia are related to choroidal neovascularization or have other physiological functions.  相似文献   
72.
Because gastric cancers located in the upper third of the stomach are difficult to detect at an early stage, the surgical results remain poor. We performed R4 gastrectomy as a radical procedure for 25 patients, involving complete resection of the latero-aortic and interaorticovenous lymph modes above and below the left renal vein, in combination with the ordinary R2 or R3 gastrectomy (the R4 group). These patients were compared with 156 others who underwent R2 gastrectomy alone (the R2 group). There were no significant differences in operation time, blood loss, or the incidence of complications between the two groups; however, when the survival rates of the patients with tumors invading beyond the subserosa were compared, the 5-year survival rate was found to be significantly higher in the R4 group than in the R2 group. Furthermore, in patients with para-aortic nodal involvement, a significant survival advantage was observed in the R4 group, as compared with the R2 group. These results suggest that the R4 gastrectomy is a rational approach for patients with advanced gastric cancer located in the upper third of the stomach.  相似文献   
73.
Endocrine tumor of the pancreas is potentially malignant. A multicenter analysis of these tumors was conducted to clarity the present status of their surgical management and the subsequent long-term surgical results. The Japan pancreatoduodenectomy (JPD) study group carried out the study; 368 patients were enrolled and variables related to tumor characteristics, surgery, and survival were retrospectively analyzed. There were 222 patients with functioning tumor and 143 patients with nonfunctioning tumor. Malignant tumor was found in 140 of 368 (38%) of the patients, and 63/140 (45%) of these patients had metastatic lesion; the most common site of the metastasis was liver 34/136 (25%), followed by regional lymph nodes 26/136 (19%). Pancreatic resection was performed in 91% of patients with nonfunctional tumor and in 83% of those with malignant tumor, and 73% of the pancreatic resections were done with lymph node dissection. The overall 5-year actuarial survival rate was 76% in patients with malignant tumor. The actuarial 5-year survival rate was 93% in the patients without metastasis and 83% in patients who received curative resection. Multivariate analysis showed that the presence or absence of synchronous metastasis was the sole significant prognostic factor. The results suggest that: (i) malignant endocrine tumor of the pancreas is a curable malignancy when pancreatic resection with lymph node dissection is adopted and (ii) that synchronous metastasis is the dominant prognostic factor. This study was carried out as a group project. The authors' institutions are as follows  相似文献   
74.
We implanted normal peripheral blood lymphocytes (PBL) from healthy donors and splenic tissues from patients with gastric cancers into the severe combined immunodeficient (SCID) mouse, demonstrating that SCID mouse with splenic tissue can produce a high level of human immunoglobulin G (IgG). The normal PBLs at 10(7) and 10(8)/mouse were implanted intraperitoneally, and three splenic tissues with a size of 3 x 3 x 3 mm from gastric cancer patients were inoculated subcutaneously into the bilateral backs of the mice. At 2, 4, 6 and 8 weeks after inoculation, mice were killed, and the human IgG was assessed by an ELISA method. SCID mice with splenic tissue revealed high human IgG levels from 2 weeks after inoculation and approximately 2 mg of IgG per ml was observed at 8 weeks post-implantation, while the IgG levels in mice treated with PBLs were limited. Since the half life of the extrinsic human IgG was 10.2 days, the high level of human IgG in the SCID mice was supposed to be produced by human plasma cells in the splenic tissue from gastric cancer patients. This model was thought to be adequate for evaluating human immunological functions in vivo.  相似文献   
75.
In order to elucidate the roles of hippocampal N-methyl-D-aspartate-type excitatory amino acid receptors in working and reference memory in rats, the effects of intrahippocampal injections of selective and competitive N-methyl-D-aspartate receptor antagonists such as CGS 19755 (cis-4-phosphonomethyl-2-piperidine carboxylic acid), 3-[(+-)-2-carboxypiperazin-4-yl]propyl-1-phosphonic acid and 2-amino-5-phosphonovaleric acid on this behavior were examined with a three-panel runway task. The results were compared with the effect of the muscarinic receptor antagonist scopolamine. In the working memory task, CGS 19755 and 3-[(+-)-2-carboxypiperazin-4-yl]propyl-1-phosphonic acid at 10 and 32 ng/side, injected bilaterally into the dorsal hippocampus before testing, produced a significant increase in the number of errors (attempts to pass through two incorrect panels of the three panel-gates at four choice points). This also occurred after the rats were given systemic injection of these drugs at 3.2 and 10 mg/kg. In the reference memory task, neither CGS 19755 nor 3-[(+-)-2-carboxypiperazin-4-yl]propyl-1-phosphonic acid affected the number of errors, whether given at doses up to 32 ng/side intrahippocampally or up to 10 mg/kg systemically. Working memory errors also increased significantly after intrahippocampal injections of d-2-amino-5-phosphonovaleric acid at 100 and 320 ng/side, but were not affected by I-2-amino-5-phosphonovaleric acid at doses up to 1 microgram/side. On the other hand, intrahippocampal scopolamine at 1.0 and 3.2 micrograms/side increased significantly working memory errors, without affecting reference memory errors.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
76.
We report the case of a 52-year-old female with middle-ear paraganglioma masquerading as a traumatic facial palsy, and describe the diagnostic steps and surgical treatment by the tympanomastoid approach.  相似文献   
77.
In a retrospective multicenter study to investigate the correlation between estrogen (ER) and/or progesterone receptors (PgR) in primary breast cancer with patient prognosis, 3118 patients with operable breast cancer (International Union Against Cancer Stages I, II, and III) were investigated from ten hospitals in Japan who underwent surgery from October 1972 to December 1982; 3089 were evaluable. The ER-positive and PgR-positive cancers were found in 56% and 34% of patients, respectively. The positivities decreased as the tumor size increased but were independent on lymph node metastasis. There were no significant differences in relapse-free survival (RFS) in relation to receptor status (median follow-up, 89 months [ER], 84 months [PgR]). However, in patients with four or more positive nodes, those with PgR-positive cancer had a longer RFS. The patients with ER-positive cancer survived significantly longer than ER-negative ones, with the greatest difference seen in those with four or more positive nodes. There was a significantly longer postrelapse survival (PRS) for patients with ER-positive cancer because of the different distribution of the major metastasis and better responses to first-line and subsequent treatments. Cox's multivariate analysis showed that overall survival but not PRS was affected by ER (and more weakly by PgR) because of the longer PRS in patients with ER-positive cancer.  相似文献   
78.
79.
To apply Nd:YAG laser irradiation through a new sapphire tip contact laser method to catheter ablation in treatment of tachy-arrhythmias, effects of laser irradiation on ventricular myocardium were investigated in 10 mongrel dogs. Nd:YAG lase (1064nm) discharges were delivered to different sites on the endomyocardium at power of 5, 10, 15, 20 or 25w with duration of 3, 5, or 10 seconds (sec.) respectively in closed beating hearts. Histopathologically, the lesion irradiated was clearly demarcated from the normal myocardium by the construction band necrosis zone. The depth of injured myocardium was less than 2mm with 3 sec. irradiations, with 5 sec. from 1 mm to 4 mm in proportion to power increase, with 10 sec. from 3mm to 8 mm in proportion to the power from 5w to 15w and could not be measured in cases of more than 20w irradiations. Although with every irradiation duration, the depth of injury increased in proportion to the power increase. With the same total energy, a longer time of irradiation produced deeper injury than a shorter time. This method makes it easier to keep the laser positioned to target than bare laser, and is suitable for use in catheter ablation.  相似文献   
80.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号